I would say the cash flow would go up every year and that would usually be the case but my son will be moving into one unit probably for just the labor to rehab the last unit (collected rent will go down for a year).After that rehab is complete, at market rent I would have about $8k/month cash flow with underwriting that most would consider conservative (for example $1200/month allocated to maintenance/cap ex). 

If we take that fact for granted -- that, for example, the average tenancy is 6 years -- then that means that some tenants stay 1 year and others stay 10 years, but when you're running numbers for a property as such then the realistic scenario is that you won't have any vacancies or turnover costs for about 6 years.

So for example if I graduate college or a few years into college I want to invest even more into real estate what do you suggest I invest in?

For example, in the New York area, especially in some hyped-up fringe neighborhoods (like certain areas of the Bronx, Queens, or Staten Island), finding a "bargain" seems easy.

I have an example, there is a client that I work with and he had never flipped before.

For example, lets say your mortgage is 4% and you take out a HELOC at 7% and draw $100k.

For example: Landlord will pay for electric, water and sewer charges up to $100 per month.

For example, one exemption is tied to your total revenue which is $5M in gross sales or receipts in a calendar year. 

For example, I have my house, am building a legal JADU, but later down the road I decide to rent my entire house and buy another primary residence.

For example, you can buy properties in the low $100k range that are already cash-flow positive or close to break-even with good tenants in place.